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98 lines
2.1 KiB
Go
98 lines
2.1 KiB
Go
package bencode
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// https://wiki.theory.org/BitTorrentSpecification#Bencoding
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import (
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"embed"
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"strconv"
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"github.com/wader/fq/format"
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"github.com/wader/fq/pkg/decode"
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"github.com/wader/fq/pkg/interp"
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"github.com/wader/fq/pkg/scalar"
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)
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//go:embed bencode.jq
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//go:embed bencode.md
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var bencodeFS embed.FS
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func init() {
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interp.RegisterFormat(decode.Format{
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Name: format.BENCODE,
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Description: "BitTorrent bencoding",
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DecodeFn: decodeBencode,
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Functions: []string{"torepr"},
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})
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interp.RegisterFS(bencodeFS)
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}
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var typeToNames = scalar.StrMapSymStr{
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"d": "dictionary",
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"i": "integer",
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"l": "list",
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"0": "string",
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"1": "string",
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"2": "string",
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"3": "string",
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"4": "string",
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"5": "string",
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"6": "string",
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"7": "string",
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"8": "string",
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"9": "string",
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}
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func decodeStrIntUntil(b byte) func(d *decode.D) int64 {
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return func(d *decode.D) int64 {
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// 21 is sign + longest 64 bit in base 10
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i := d.PeekFindByte(b, 21)
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if i == -1 {
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d.Fatalf("decodeStrIntUntil: failed to find %v", b)
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}
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s := d.UTF8(int(i))
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n, err := strconv.ParseInt(s, 10, 64)
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if err != nil {
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d.Fatalf("decodeStrIntUntil: %q: %s", s, err)
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}
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return n
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}
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}
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func decodeBencodeValue(d *decode.D) {
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typ := d.FieldUTF8("type", 1, typeToNames)
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switch typ {
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case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9":
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d.SeekRel(-8)
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length := d.FieldSintFn("length", decodeStrIntUntil(':'))
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d.FieldUTF8("separator", 1, d.StrAssert(":"))
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d.FieldUTF8("value", int(length))
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case "i":
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d.FieldSintFn("value", decodeStrIntUntil('e'))
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d.FieldUTF8("end", 1, d.StrAssert("e"))
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case "l":
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d.FieldArray("values", func(d *decode.D) {
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for d.PeekUintBits(8) != 'e' {
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d.FieldStruct("value", decodeBencodeValue)
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}
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})
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d.FieldUTF8("end", 1, d.StrAssert("e"))
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case "d":
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d.FieldArray("pairs", func(d *decode.D) {
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for d.PeekUintBits(8) != 'e' {
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d.FieldStruct("pair", func(d *decode.D) {
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d.FieldStruct("key", decodeBencodeValue)
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d.FieldStruct("value", decodeBencodeValue)
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})
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}
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})
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d.FieldUTF8("end", 1, d.StrAssert("e"))
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default:
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d.Fatalf("unknown type %v", typ)
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}
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}
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func decodeBencode(d *decode.D) any {
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decodeBencodeValue(d)
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return nil
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}
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